In the field of photographic processing services, color printing systems for obtaining color prints from color negatives, reversal photosensitive materials and digital cameras have come into widespread use recently in not only laboratories dedicated to print processing (color processing laboratories) but also photo processing shops. As to the exposure methods adopted in these color printing systems, the method of launching rays of light incident on photographic film, such as color negative, into color paper and subjecting the photographic film to mask exposure, or the so-called direct (analog) exposure method, used to be in the mainstream. In recent years, however, printing apparatus utilizing digital exposure capable of obtaining color prints from digital cameras, more specifically the digital exposure system in which images recorded on films are read optoelectronically, the information of the thus read images are converted to digital signals, the digital signals are subjected to image processing, and images are recorded by scanning exposure with recording light modulated in accordance with the image data, has been put to practical use, and further it is becoming pervasive.
In a color printing system utilizing such a digital exposure method, a photosensitive material is wound into a roll and loaded in a cartridge with a taking-out slit, which is referred to as a magazine. At the time of use, the roll-form photosensitive material is pulled out of the slit and transported, subjected to exposure and photographic processing as it kept its roll form without being cut during the transport, and after drying it is cut into sheets with the intended length. In this process, or the so-called roll transport method, color prints has so far been made. This method requires a photosensitive material to form frame information for showing explicitly boundaries for each sheet of print. The areas for frame information become wastes.
Only lately, therefore, color printing systems adopting a sheet transport method wherein a photosensitive material is cut in a print size and formed into sheets, and then subjected to exposure and photographic processing, has entered into practical utilization. In such a sheet transport method, a photosensitive material cut into sheets is transported in a condition that uneven scanning exposure is avoided from occurring by adopting two ways of transporting, one involving the use of transport roller pairs and the other involving the use of a conveyor belt, and thereafter subjected to photographic processing. In the photographic processing, sheet-form photographic materials are transported by transport roller pairs. It is desirable that such a color printing system can deliver prints in great numbers per hour, and it is preferable that this highly productive system is implemented in comparatively compact apparatus. Therefore, the tendency now is proceeding toward replacement of the transport system for photographic processing with a system having a faster transport speed than previous systems.
However, such an increase in the transport speed requires a color photosensitive material, or color paper, to have more suitability for high illumination intensity exposure, higher processing consistency and higher ability to be processed rapidly than ever. In order to satisfy these requirements, the photographic industry has carried out studies on improvements in reciprocity characteristics of silver halide emulsions, improvements of couplers and coupler dispersions with the aim of developing colors by efficient coupling reaction of couplers with oxidized color developing agents, and improvements in the design of a photosensitive material in its entirety, inclusive of the constituents as described above. Although much effort has already been made in order to achieve the aforementioned improvements, it is to be desired that still more improvements from the aspects of both photosensitive material and processing system are made to satisfy further enhanced productivity and operability requirements of color photographic processing systems.
In the photographic processing service industry, photographic light-sensitive materials capable of being processed rapidly and offering high image quality have also been requested in recent years as part of a customer service improvement and as a measure of productivity improvement. In order to meet this request, it is generally carried out at present to subject photographic light-sensitive materials containing emulsions with high silver chloride contents (hereinafter referred to as print materials high in silver chloride content) to color development-processing (e.g., Color Processing CP-48S made by Fuji Photo Film Co., Ltd.). However, even the rapid processing systems using print materials high in silver chloride content are still difficult to say that their processing rapidity is satisfactory and comparable to rapidity of color image formation by other systems (e.g., an electrostatic transfer system, a thermal transfer system, an inkjet system). Therefore, it is desired to reduce the total processing time of a print material high in silver chloride content, extending from the start of development to the end of drying. Further, from the viewpoint of performance consistency in continuous processing, it is hard to say that the system of using print materials high in silver chloride content is superior to other systems for color-image formation. Therefore, improvement in robustness against performance variation by continuous processing has so far been required of such print materials. Furthermore, it sometimes happens that processing solutions are sequenced in poor conditions during continuous processing, and a density variation occurs within each sheet of the prints obtained under such conditions. Accordingly, improvement in robustness of each individual print is also required.
Under these circumstances, various studies and effort to develop methods for improving continuous processing consistency have been made in this industry.
For forming color photographic images, photographic couplers capable of forming three colors, yellow, magenta and cyan, are incorporated into three types of light-sensitive layers differing in color sensitivity, respectively, subjected to imagewise exposure, and then processed with a color developer containing a color developing agent. In this process, the couplers provide color-developed dyes by coupling reaction with the oxidized aromatic primary amine. In general the processing process of silver halide color photosensitive materials includes a color-developing step for forming color images, a desilvering step for removing developed silver and undeveloped silver, and a washing and/or stabilizing step. In the desilvering step for removing developed silver and silver halides, the developed silver is re-oxidized by a bleaching agent and fixation is carried out using an agent for solubilization of silver halides. These operations may be performed in successive steps using a bleaching solution and a fixing solution individually or in one step using a single solution containing a combination of a bleaching agent and a fixing agent. The latter solution is generally referred to as a blix solution.
As a silver bleaching agent in the bleaching solution and the blix solution, iron(III) complex salts of organic acids, especially iron(III) complex salt of ethylenediamine-N,N,N′,N′-tetraacetic acid (hereinafter abbreviated as “PDTA”), are generally used. In addition, iron(III) complex salt of 1,3-propanediamine-N,N,N′,N′-tetraacetic acid (hereinafter abbreviated as “PDTA”) is also widely used from the viewpoints of an increase in processing speed and a reduction of waste ingredients in processing solutions. On the other hand, growing awareness about environmental conservation has aroused a lively concern for discharge of the aforementioned chelating agents having not only low biodegradability in the natural world but also a tendency to render deleterious heavy metal ions soluble. As a result, development of alternatives to the chelating agents mentioned above has been required. In response to this requirement, the chelating agents high in biodegradability are disclosed in JP-A-4-313752, JP-A-5-265159 and JP-A-6-161065.
However, the use of such iron(III) complex salts as bleaching agents for color photography sometimes causes a failure of cyan dye images to have sufficient densities. This phenomenon is generally recognized as reduction discoloration by conversion of cyan dyes into leuco compounds in bleaching or blix solutions (and referred to as blix discoloration). U.S. Pat. No. 4,591,548 indicates that the presence of iron(II) complex salts in bleaching or blix solutions becomes a cause of conversion of cyan dyes into leuco compounds.
The blix solutions are in an oxidative atmosphere, and can more effectively achieve their effect by supplying the processing solution with oxygen from the air. Moreover, oxidation of iron(II) complex salts present in the processing solutions makes it possible to prevent the cyan density from decreasing, or to avoid blix discoloration from occurring. From these points of view, blix discoloration can be lessened by expanding the air-contacted area of the processing solution in a blix processing tank, or the so-called aperture rate. However, the expansion of the aperture rate promotes vaporization of water at the time of continuous processing and heightens concentrations of ingredients in the processing solution; as a result, a precipitation problem occurs in some cases. Therefore, it is required to stabilize the cyan density in a processor having a blix bath low in aperture rate. In this respect, a solution by improvements on the side of a silver halide color photographic material is also awaited.
On the other hand, it has been aimed at in recent years to simplify and speed up photographic processing for color photographs by reductions in replenishment rate and processing time. Decreased replenishment and increased availability rate in the desilvering step give rise to an increase of the iron(II) complex salts and foster a tendency to worsen blix discoloration. In addition, the processing time in the desilvering step can be reduced effectively by lowering the pH of a bleaching solution or a blix solution. However, the lowered pH of the bleaching solution or the blix solution results in a drawback of promoting blix discoloration of cyan dyes, too.
With the intention of overcoming the blix discoloration of cyan dyes, a wide variety of approaches as mentioned below have been proposed. For instance, the improvement by modifying the concentration and the composition of a bleaching solution or a blix solution are disclosed in U.S. Pat. No. 3,706,561. The reduction in the total silver coverage of the layers arranged underneath the cyan dye-forming layer in a color photographic element is proposed in U.S. Pat. No. 4,366,233. The improvements by various compounds in a processing bath are disclosed in U.S. Pat. No. 3,820,997. The addition of water-soluble ionic compounds containing polyvalent elements to a blix bath is proposed in U.S. Pat. No. 3,774,510. The cyan couplers suitable for overcoming the foregoing troubles are disclosed in U.S. Pat. Nos. 4,151,680, 4,374,922 and 4,591,546.
As a method of improving the blix discoloration, the method of making improvement by use of hydroquinone or certain quinone derivatives is disclosed, e.g., in JP-A-63-316857. However, these previous arts have defects that effects thereof are insufficient, or while admitting their effects they sacrifice photographic properties, such as keeping quality of images, or a heavy load is imposed on liquid waste disposal. Further, those previous arts cannot bring about satisfactory solutions in the cases of the blix solutions using not only the EDTA-iron(III) complex salts or the PDTA-iron(III) complex salts but also the iron(III) complex salts of biodegradable chelating agents. Therefore, arts of producing greater effects on prevention of blix discoloration of cyan dyes without attended by the drawbacks as mentioned above have been required in recent years from the viewpoints of speedup of processing and influences upon environments.
On the other hand, attempts to improve blix discoloration of cyan dyes by use of polymer latices have so far been made. For instance, JP-A-64-52136 and JP-A-2-289840 disclose the methods of using polymer latices having alkoxyalkyl groups in side chains of their respective polymers. However, even these polymer latices are insufficient in their effects against blix discoloration. Accordingly, performance enhancement is required, especially in the cases of simple-and-rapid processing carried out under low-replenishment conditions. In addition, the polymer laticies of the foregoing type are of inferior dispersion stability.
Polymer latices prepared by copolymerizing monomers having —COOH groups are also well known in the field of photographic materials. For instance, the copolymer of n-butylacrylate and acrylic or methacrylic acid is disclosed in U.S. Pat. No. 3,287,289. In addition, JP-A-11-84559 discloses that the improving effect is enhanced by rendering the pH of coating compositions acidic. Yet it cannot be said that the improvement attained thereby is on a satisfactory level.
Even into the field of performing color printing by use of color photographic paper, recent years has seen a remarkable penetration of digitization. For instance, digital exposure systems utilizing laser-scanning exposure have enjoyed a leap increase in dissemination rate, compared with traditional analog exposure systems performing direct printing from exposed color negative films by means of a color printer. These digital exposure systems are notable for image quality heightened by image processing, and play an important role in improving the quality of color print using color photographic paper. Further, as digital camera penetration increases explosively, it is also becoming an important factor that color prints of high quality can be obtained with ease from such electronic recording media, and these circumstances are thought to result in a dramatic proliferation of digital exposure systems.
On the other hand, technologies for an inkjet system, a sublimation-type heat-sensitive transfer system and an electrostatic color photographic system each have made their individual progresses and have come to speak of the quality of photographs; as a result, they are being recognized as color printing systems. Of the color printing systems, the digital exposure systems using color photographic paper have features including high quality, high productivity and images with high fastness, and it is to be hoped that these features are further expanded and photographs of higher quality are provided more easily at lower prices. If a rapid finish service that the recording medium of a digital camera is received from a customer over the counter, high-quality prints are finished in a short time of the order of several minutes and the finished prints are instantly handed on to the customer, the so-called one-stop service of color prints, becomes feasible, the superiority of color prints using color photographic paper becomes more pronounced. In addition, if the rapid processing suitability of color photographic paper is enhanced, it becomes feasible to use printing equipment which is highly productive although it is smaller in size and lower in price. As a result, it can be expected that one-stop service of color prints becomes more widely available. In this respect, it is desired to enhance the rapid processing suitability of color photographic paper in particular. Further, the development time shortened by enhancing the rapid processing suitability of color print results in reduction of passage times of color photographic paper through processing solutions, and enables processing tanks to be downsized so long as the setting of the transport speed of color photographic paper is not changed. In order to counter the color printing systems other than the systems of using color photographic paper, the downsizing of equipment becomes important. From this viewpoint also, it is significant to enhance the rapid processing suitability of color photographic paper.
In order to enable one-stop service of color prints using color photographic paper, it is required to conduct studies from various points of view, inclusive of reduction in exposure time, reduction in a time period from the conclusion of exposure to the start of photographic processing, or the so-called latent-image time, and reduction in a time period from photographic processing to drying. Hitherto, proposals have been made from the foregoing viewpoints respectively. Of those points, the time required for exposure of one sheet of print is very short, compared with the other times, so it is no problem in the case of printers of normal power which are generally used in photo processing shops. As to the latent-image time, on the other hand, printers are designed so as to reduce the latent-image time to a minimum. In addition, reduction in the time period from processing to drying has also been tried. Specifically, various proposals have been put forth to effect rapid processing by putting ideas into designing processing compositions and setting processing temperatures and stirring conditions of processing solutions, or by devising ways to squeegee and dry photosensitive materials.
As a usage pattern of color photographic paper, it is common to adopt the so-called roll transport method in which roll-form color photographic paper is exposed and processed as its roll form is kept, and cut into sheets after the processing. In addition to such a transport method, color printing systems adopting a sheet transport method, in which photographic paper is cut into sheets of a print size before exposure and the sheets of photographic paper are exposed and processed, have put to practical use in recent years. Since it is required for photographic paper to form frame information for showing explicitly boundaries between juxtaposed prints, this transport method is undesirable in the sense that the areas for frame information are useless and become wastes. On the other hand, the sheet transport method has an advantage in that the foregoing problem is already settled. However, the sheet transport system requires photographic paper sheets to be transported while nipping them by pairs of transport rollers; as a result, it sometimes occurs that the pressure between a pair of rollers causes image defects, such as fogging in image areas and sensitivity modification streaks (streak-form unevenness in density which arises from increase in density by sensitization and decrease in density by desensitization). As a result of our examination, it has been found that sensitization streaks developed especially by the pressure imposed on the exposed photographic paper in a state of being dipped in a processing solution became more remarkable the more the transport speed was increased and the shorter the time period from the conclusion of exposure to the start of development was made for rapid processing. Further, our examination has revealed that these sensitization streaks were amplified by the use of a highly active developer enabling short-time development at relatively high temperatures and became a serious problem. Furthermore, it has been found that the sensitization streaks became more pronounced in the case of using photosensitive materials stored in an unexposed state after producing them than in the case of using photo sensitive materials just after the production thereof. Therefore, it is desired to develop technologies for improving the pressure sensitization streaks which become more pronounced in the case of subjecting color photographic paper to the rapid processing utilizing a sheet transport system. In addition, it is also hoped that technologies enabling improvement of pressure sensitization streaks not only just after production but also after storage of photosensitive materials will be developed.
In response to the request for rapid processing suitability, silver halide emulsions used in color photographic paper are emulsions having high silver-chloride contents. There is disclosure of incorporation of various metal complexes into such silver halide emulsions as to have high silver chloride contents. For the purpose of improving high illumination intensity failure of silver chloride emulsions and obtaining hard gradation under high illumination, it is known to dope the emulsions with Ir complexes. For instance, JP-B-7-34103 discloses that the problem of latent-image sensitization is solved by providing a localized phase having a high silver bromide content and doping the phase with an Ir complex. U.S. Pat. No. 4,933,272 discloses that low illumination intensity failure can be reduced by incorporation of a metal complex containing NO or NS in its ligands. U.S. Pat. Nos. 5,360,712, 5,457,021 and 5,462,849 disclose that reciprocity law failure can be reduced by incorporating metal complexes containing particular organic ligands as a part of their respective ligands. In addition, U.S. Pat. Nos. 5,372,926, 5,255,630, 5,255,451, 5,597,686, 5,480,771, 5,474,888, 5,500,335, 5,783,373 and 5,783,378 disclose that properties of emulsions having high silver halide contents, including reciprocity law characteristics, can be improved by use of combinations of Ir complexes and metal complexes containing NO in their respective ligands. JP-A-2000-250156, JP-A-2001-92066 and JP-A-2002-31866 disclose the emulsion arts of ensuring excellent latent image stability after exposure by combined use of Ir complexes and Rh complexes.
JP-A-58-95736, JP-A-58-108533, JP-A-60-222844, JP-A-60-222845, JP-A-62-253143, JP-A-62-253144, JP-A-62-253166, JP-A-62-254139, JP-A-63-46440, JP-A-63-46441, JP-A-63-89840, and U.S. Pat. Nos. 4,820,624, 4,865,962, 5,399,475 and 5,284,743 disclose that high sensitivities can be achieved by incorporating phases high in silver bromide content and various in form into emulsions having high chloride contents so that the phases are present in localized states.
U.S. Pat. Nos. 5,726,005 and 5,736,310 disclose that increase in sensitivity and reduction in high illumination intensity failure can be attained with the emulsions having high chloride contents and containing iodide in a state of having the concentration maximum at the sub-surface of emulsion grains. In the examples of EP-A-0928988, it is disclosed that emulsions having excellent characteristics with respect to reciprocity law failure, temperature dependence upon exposure and immunity to pressure can be obtained by incorporating the specified compounds into I-band forming grains at the time when 93% of grain formation is accomplished.
In JP-A-10-123658 and JP-A-11-282114, it is disclosed that the pressure fog developed in the case of imposing pressure on color paper dipped in a developer can be improved by use of the specific disulfide compounds and the photographic emulsions containing silver iodochloride sensitized chemically under the specified condition and further having the specific mercapto or metallic compounds.
However, those known arts are silent on improvement of sensitization streaks developed by pressure imposed on sheet-form color photographic paper after exposure in the case where the sheet-form color photographic paper undergoes color development in a short time falling within 28 seconds as it is transported at a high speed.